Electric grounding plug



Feb. 9 1926. 1,572,079

0. D. PLATT ELECTRIC GROUNDING PLUG Filed Sept. 18', 1923 Patented Feb. 9, 1926.

UNITED STATES CLARENCE D. PLATT, OF BBIDGEPORT, CONNECTICUT.

ELECTRIC GROUNDING PLUG.

Application filed September 18; 1923. Serial No. 663,324.

, To all whom it may concern Be it known that I, CLARENCE D. PLATT, a citizen of the United States of America, residing at Bridgeport, county of Fairfield, Connecticut, have invented a new and useful Electric Grounding Plug, of which the following is a specification.

Modern practice requires in many cases that electric lines be grounded. This is conveniently accomplished by plugs adapted to be inserted in, place of ordinary fuse plugs.

The main object of my invention is to provide a simple, inexpensive plug which can be readily inserted to ground a line but which cannot be removed by the use of an ordinary screwdriver. Another object is to provide a plug of this character which is not permanentl attached but which can be readily remove by a special tool so that the dummy or grounding plug may in case of necessity be removed in order to substitute a fuse plug. 1 The dummy plug is so construct ed that it maybe readily screwed in place by the use of an ordinary screw driver, but it cannot be unscrewed with a screw (l1'lVBI\ or removed except by an authorized person having the special tool or key. I

Figure 1 is a perspective view of an ordinary duplex block with a fuse plug and a grounding plug in place.

Fig. 2 is a transverse sectional view showing .the grounding plug in place.

Fig. 3 is a perspective view of the inner portion or body lining of the grounding p Fig. 4 is a plan view of the same.

ig. 5 is a perspective view of a combined screw driver and special tool or key for inserting or moving the plug.

Fig. 6 is a transverse sectional view' of one form of my improved plug.

Fig. 7 is an enlarged sectional view of the plug, the section being taken on a plane at right angles to the section of Fig. 6 and showing the tip of an ordinary screw-driver in place.

The block 7 is typical of any suitable form of construction having one or more receptacles, each of which has a screw shell or socket 8 and a center contact 9 connected to suitable circuit terminals. 10 indicates a typical fuse plug and 11 indicates one of my improved grounding plugs.

The grounding plug consists of two parts, namely the interior or body member 12 formed of some suitable lnsulating material such as porcelain and the outer shell or eas--- ing 13 of. some suitable metal the edges 14 of which grip or embrace the upper edge of the body 12 to hold the parts together. The metal part may have one or more bosses 15 indented into recesses in the body to prevent relative rotation of the two parts of the plug. I

The outer end of the body 12 of the plug is provided with specially formed recesses which furnish oppositely disposed shoulders 16 to be engaged by a screw driver' in screwing the plug into the socket 8. Oppo-. site each of these shoulders 16 is a cam surface- 17 so inclined that a screw driver will find no abutting shoulders when it is rotated anticlockwise-but the end of the screw driver will slide up the inclines and away from the shoulders 18. It is thusimpossible to unscrew the plug with an ordinary screw driver or similar tool. It sometimes happens however that it is necessary or desirable for an authorized person to remove the plug without destroying the plug or socket 8. I therefore prefer to provide oppositely disposed recesses 18 adjacent the shoulders 16 into which the prongs of a bifurcated instrument may be inserted for the purpose of rotating the plug backward and removing it from the socket 8 or the. like.

Figure 5 shows a tool which may be formed like a. screw driver at the end 19, to engage the shoulder 16 for seating the grounding plug or for any other purpose. The opposite end 20 of this instrument is bifurcated so as to have prongs adapted to c tend into therecess 18 and enable the holder of the key or instrument to unscrew the plug when desired. Of course it will be noted that the plug might be either seated or unseated by the use of the key in Fig. 5 provided the prongs were inserted in the recesses 18. Neither of the recesses 18 however is large enough or so constructed as to receive an ordinary screw driver or similar tool. The bottom 21 of thebody is preferably so constructed as to be seated in the bottom of the casing or shell 13 so as to reenforce the same when the plug is being seated and avoid denting or distortlon which might occur in the very thinmetal should there be any space between the metal and-the lining at this point.

I claim:

l. A plug having" oppositely disposed screw driver engaging shoulders, driver disengaging inclines between v the shoulders, and oppositely disposed key re 'ceiving recesses between the inclines.

2. A plug having abody with open key receiving recesses disposed onopposite sides of the center to permit the plug to be turned by a special key, and shoulders permitting the plug to be turned in one direction by an ordinary screw driver but rendering the screw screw driver incapable of turning the plug end with oppositely-disposed shoulders to permit, the plug to be inserted by an ordinary screw-drivenand having oppositelydisposed inclined cam surfaces to disengage said screw-driver when attempting to unscrew the plug, said body also having rccesses to receive a special tool for unscrewing said plug.

CLARENCE D. PLATT. 

